The T-even bacteriophage E. coli system has been investigated as a model for viral invasion, viral structure and viral assembly. It has been found that the product of T4D gene 12 is a zinc metallo-protein which constitutes the short tail fibers of the phage baseplate. Investigations are continuing in the biological role of this viral zinc protein and the role it plays during injection of the viral DNA. In addition, the structural role of the phage tail-plate folate is being studied. It has been found that the product of T4D gene 28 is a folic acid conjugate. This protein has been partially purified and characterized.